Imaging modalities and physics: ghosting artefact: practice question

A Radiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Radiology · Imaging modalities and physics: ghosting artefact

Sample item

On a sagittal spine MRI, pulsation of the aorta produces repeated ghost images that overlie the spinal cord. Which simple change moves the ghosts away from the cord without altering the anatomy imaged?

ALower the receiver bandwidthBShorten the echo timeCIncrease the slice thicknessDSwap the phase-encoding and frequency-encoding directions

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Swap the phase-encoding and frequency-encoding directions

Motion ghosts propagate along the phase-encoding direction, so swapping the phase and frequency axes relocates them. Slice thickness, echo time and bandwidth do not change the axis along which ghosts appear.

Option by option

A. Lower the receiver bandwidth
A lower bandwidth increases chemical shift and noise and leaves ghost direction unchanged.
B. Shorten the echo time
A shorter echo time reduces some flow dephasing but does not move the ghosts.
C. Increase the slice thickness
A thicker slice changes resolution and signal, not the direction of ghost propagation.
D. Swap the phase-encoding and frequency-encoding directions (correct)
Correct. Ghosts spread along the phase axis, so swapping axes relocates them.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is D, Swap the phase-encoding and frequency-encoding directions. Motion ghosts propagate along the phase-encoding direction, so swapping the phase and frequency axes relocates them.

Why is "Lower the receiver bandwidth" not the answer?

A lower bandwidth increases chemical shift and noise and leaves ghost direction unchanged.

Why is "Shorten the echo time" not the answer?

A shorter echo time reduces some flow dephasing but does not move the ghosts.

Why is "Increase the slice thickness" not the answer?

A thicker slice changes resolution and signal, not the direction of ghost propagation.

What concept does this question test?

It tests Imaging modalities and physics: ghosting artefact in Radiology. Slice thickness, echo time and bandwidth do not change the axis along which ghosts appear.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Imaging modalities and physics: ghosting artefact?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.